Subgenus PARAHELODON Peterson

Helodon decemarticulatus (Twinn)

Rothfels (1956, description; drawing of IIIS; photo of partial chromosome II; pericentric fixed inversion): [Canada]

Rothfels & Mason (1975, photo of male achiasmate meiosis): [North America]

Rothfels (1979, cytodendrogram, recognition of 2 sibling species [unnamed]): North America

Helodon gibsoni (Twinn)

Rothfels (1956, description, drawing of IIIS, photo of partial chromosome II): [Canada]

Rothfels & Mason (1975, absence of male achiasmate meiosis): [North America]

Rothfels (1979, cytodendrogram, recognition of 2 sibling species [unnamed]): North America

Helodon vernalis Shewell

Rothfels (1979, cytodendrogram, whole-arm interchange [arm associations not specified]): North America